From: Sam Roberts <sroberts@...>
Date: 2006-04-13T07:14:41+09:00
Subject: Re: Simple substitutions

On Wed, Apr 12, 2006 at 08:58:17PM +0900, Peter Bailey wrote:
> I have a need to parse postscript print files on a daily basis. Some of 
> them are over 10 mB. One thing I need to find out is the number of pages 
> in the files. There's a simple one-liner at the top of each .ps file 
> that states the number of pages. It reads:
>                              %%Pages: xx
> It's a line of its own.
> 
> I simply want to find that line in my source file and then write a 
> corresponding line in my output file:
>                              Number of pages: xx
> 
> I tried the following in IRB, but I get the syntax error shown below.
> 
>      File.open("psout.txt", "w") do |output|
>        File.foreach("test1.ps") do |line|
>          line.sub!(/\%\%Pages: ([0-9]{1,5})/"Pages: \1"/)

Other people commented on the regex

>          output << line

For efficiency, you can do:

   if(line =~ /%%Pages: (\d+)/)
	  output << $1
	  break
   end

YMMV, but stopping processing the file as soon as you've found what you
want is faster.

Sam